The device for mixing two pasty substances, particularly for mixing a dental impression substance with a catalyst substance, comprises a housing with a substantially tubular portion. At least two inlet openings (68) for the two pasty substances are arranged at the rear end of said housing, and an outlet opening for the mixed pasty substances is arranged at the front end of said housing. The housing comprises a coupling portion joining the tubular portion and having two coupling openings for connecting the housing with two outlet openings of a device for dispensing the two pasty substances. The coupling openings are connected to the inlet openings (68) via first and second channels (64,66) extending through the coupling portion. At least one mixer element is arranged within the tubular portion of the housing for mixing the two pasty substances when the substances are passing through the tubular portion of the housing. The first channel (64) or the second channel (66) or both channels (64,66) extend to at least two inlet openings (68). All inlet openings (68) are spatially separated from each other. The first channel(s) (64) is (are) separated from the second channel(s) (66).